Gas blast electric circuit breaker



2, 194-2. R M, BENNETT GAS BLAST ELECTRIC CIRCUIT BREAKER Filed Aug. 22, 1941 6A5 BLAST EXHAusT MW w 1% m iw nBQ% e J g TmwWH Patented June 2, 1942 GAS BLAST ELECTRIC CIRCUIT BREAKER Robert M. Bennett, Ithan, Pa., assignor to Gen eral Electric Company, a corporation of New York Application August 22, 1941, Serial No. 407,866

7 Claims.

My invention relates to gas blast electric circuit breakers, and particularly to those of the cross-blast type wherein the are to be interrupted is formed in a narrow elongated insulating passage at the entrance portion of an arc chute where it is subjected to a substantially transverse blast of interrupting gas directly through the passage and into the arc chute.

The principle object of my invention is the.

provision of an improved circuit'breaker of the aforesaid type that is more effective in its application of the interrupting blast to the are within the aforesaid passage at a given gas supply pressure.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. l is an elevational view in section of a cross-blast electric circuit breaker embodying the present invention in the open circuit position thereof, and Fig. 2

is an enlarged view of a part of the circuit breaker taken in section along the line 2-2 of Fig. 1.

The air circuit breaker illustrated by way of example in Fig. 1 is of the cross-blast type and comprises the conductor terminals l and 2 to which the coacting contacts 3'and 4 are connected respectively. The contact 4 which is in sliding contact with terminal 2 comprises a reciprocally movable blade-like member arranged to engage the finger contacts 3 of the stationary contact. The movable contact is suitably controlled and operated by mechanism not shown and the fixed contact is mounted in an insulating casing 5 defining the arc chute.

The casing or chute 5 comprises spaced insulating sidewalls B 'coacting with insulating diverging end walls .1 to form a narrow ianshape are chute leading from the coacting contacts. The contacts themselves separate within a narrow elongated passage hereinafter described with more particularity defined by insulating material composed preferably of hard fibre or the like. This passage is in communication with an air supply conduit 8 which is arranged to be connected to a suitable source of gas or air pressure, such as a reservoir supplied from a compressor unit (not shown). The control means for admitting air under pressure to the arc chute upon separation of the contacts form no part of the present invention and are omitted in the interest of simplicity.

Suitable arc extinguishing means, such as hard fibre barriers 9, extend fan-wise from the arc path between the insulating sidewalls 6 so as to divide the arc chute into a plurality of diverging passages. An additional insulating fibre barrier I 0 extends continuously throughout the arc chamber with the exception of a slot ID in registry with and of suilicient size to receive the blade contact I. The extinguishing structure including the barriers 9 and I0 is composed of a suitable organic vaporizable material that does not lose its dielectric strength in the presence of the arc.

.In the arrangement so far described, admission of an air blast to the entrance of the arc chamber at il in accordance with separation of the contacts is effective to drive the are which forms between the extended stationary finger contacts 3 and the arcing tip 4 of the movable contact into the arc chute passages so as to impinge directly on the exposed edges of the fibre barriers 9. As the hot blast flowing from the region of the arc is directed into the diverging chute passages, it soon encounters cooling structure constituting spaced copper plates [2 extending across the path of gas flow. This cooling structure is intended to reduce the temperature and the volume of the highly heated blast gases so as to minimize back pressure, and, in the case of moderate current interruptions, prevent flame emission from the chute exhaust. Flame emission at the chute exhaust can be further reduced or prevented by a conduit 13 arranged to vent the chute gases laterally as indicated.

An air blast circuit breaker of the general character above described is disclosed and claimed in an application Serial No. 303,126, filed November 6, 1939, by D. C. Prince et al. for Circuit breaking apparatus and method of operating the same," and assigned to the same assignee as the present invention.

Although the air blast circuit breaker of the aforesaid Prince et al. application has been very successful in interrupting, for example, 15 k. v. power circuits 0! high amperage, I have found that the interrupting performance of this type ,breaker can be still further improved by modifying the design of the arc passage wherein the arc is first subjected to the interrupting blast so that the leading edge of the contact blade (considered with reference to the interrupting gas flow) is within a constricted part of the passage (referring to the transverse cross-sectional area) and the trailing edge, at which the arc preferarcing time at a gas supply pressure appreciably lower than required for previous breakers. For example, a cross-blast circuit breaker embodying my invention was able consistently to interrupt high voltage power currents at the first current zero after parting of the contacts with a gas supply pressure of 70 pounds per square inch, as contrasted with a gas supply pressure of 110 pounds per square inch required by the prior type breaker for the same interrupting performance.

A practical embodiment of my invention is illustrated by Fig. 2, taken in connection with Fig. l. The elongated arc passage il in which the arc forms upon separation of the contacts is bounded by diverging insulating side walls comprising spaced blocks i4 and ii of horn fibre, or the like, suitably mounted as indicated at the chute entrancebetween the chute side walls 6 and the end wall 6. The block sides I4 and I respectively are tapered as illustrated so that the leading edge of the blade contact 4 is closely confined between the blocks and the trailing edge at 4' is positioned in a widened or flared part of the passage. The generally V-shape passage so formed is still further widened and flared for an appreciable distance beyond the blade contact where it merges into the main part of the arc chute. In order to avoid too drastic restriction of the gas supply, the passage side walls opposite each other at 8' are provided with grooves forming in effect an extension of the blast supply conduit 8.

defining an elongated passage in which said blade contact is longitudinally movable to form said arc gap, and means for directing a blast of interrupting gas through said passage in a direction substantially transverse 'to the longitudinal axis thereof and to said are gap, said blade contact being disposed edgewise to said blast, the insulating side walls of said passage diverging from the leading or blast-impinging edge of said blade contact so that the trailing edge thereof is disposed in a comparatively wide flared part of said passage, said contacts being formed so that the arc to be interrupted is formed in the aforesaid flared part of said passage.

With my improved arc chute, the interrupting I blast acts with more intensity on the arc to ininsulating arc barriers 9 are preferably spaced a short distance as indicated from the upper or trailing edge of the blade contact so that, even after slight separation of the contacts, there is immediate relief for the arc gases, and consequently immediate application of the interrupting blast. I have found that this spacing should be approximately for best results in interrupting large overload or short circuit currents.

The operation of my improved circuit breaker is now believed to be apparent from the foregoing description; When the blade contact 4 is drawn to the position shown to open the circuit, the interrupting gas is admitted to the conduit 8 so as to cross the arc path immediately upon its formation. In the case of high current arcs, considerably back pressure may be caused by the arc itself and this back pressure may in certain cases greatly impede the interrupting blast. In the present case, however, the arc is drawn between the arcing tips 3' and 4' inthe flared 2. A gas blast circuit breaker comprising relatively movable contacts including a movable blade-like contact, insulating structure defining an elongated passage in which said blade contact is reciprocally operated to form an arc gap and which partially encloses said blade contact in sheath-like manner, means for directing a blast of interrupting gas at high velocity through said passage in a direction substantially transversely of the longitudinal axis thereof so as to traverse the arc gap, said blade contact being disposed edgewise to said blast, the insulating side walls 1 of said passage being closely positioned with respect to the blast-impinging leading edge of said blast contact and diverging from said edge so that the trailing edge of said'blade contact is positioned in a comparatively wide part of the passage, and means for causing the interrupting arc to attach itself at said trailing edge of said blade contact whereby the arc is subjected to the interrupting blast in the aforesaid wide part of the passage.

3. A gas blast circuit breaker comprising relatively movable contacts separable to form an arc gap, one of said contacts being of blade-like shape and movable to open the circuit, insulating arc chute structure defining an elongated passage at the entrance part of the chute in which said blade contact is longitudinally movable to form said are gap, means for directing into said chute a blast'of interrupting gas through said passage in a direction substantially transverse to the longitudinal axis thereof and to said arc gap, said blade contact being disposed edgewise to said blast, the insulatingside walls of said passage extending generally along the lateral sides of the blade contact diverging from the blast-impinging or leading edge of said blade contact so that the trailing edge thereof is disposed in a comparatively wide fiared part of said passage leading to the chute interrupting structure, said contacts being formed so that the arc to be interrupted is positioned in the aforesaid flared part of said passage.

4. A gas blast circuit breaker comprising relatively movable contacts separable to form an arc gap, one of said contacts being of blade-like shape and movable to open the circuit, insulating arc chute structure defining an elongated sheath-like passage in which said blade contact is longitudinally movable to form said are gap,

said chute structure also including insulating arc barriers disposed along said are gap in transverse edgewise relation thereto so as to form in the chute separate gas passages leading from said are gap, means for directing a blast of interrupting gas through said sheath-like passage in a direction substantially transverse to the longitudinal axis thereof to cross said arc gap and drive the arc against the adjacent barrier edges, said blade contact being disposed edgewise to said blast,

the insulating side walls of said passage extending along the lateral sides of the blade contact being closely adjacent to the blast-impinging edge of said blade contact and diverging therefrom so that the trailing edge thereof is disposed in a comparatively wide flared part of the generally V-shape passage so formed, said blade contact being arranged so that the arc to be interrupted is positioned in the aforesaid flared part of said passage and the trailing edge of said blade spaced from the adjacent barrier edges a distance sufficient to prevent material arc backpressure due to accumulation of arc gases in said sheath-like passage.

5. A gas blast circuit breaker comprising relatively movable contacts including a movable blade-like contact, insulating arc chute structure defining an elongated passage at the en- 'trance part of the chute in which said blade contact is reciprocally operable to form an arc gap and which partially encloses said blade contact in sheath-like manner, means for directing a blast of interrupting gas at high velocity through said passage in a direction substantially transversely of the longitudinal axis thereof to traverse the arc gap, said blade contact being disposed edgewise to said blast, the insulating side walls of said passage comprising a pair of blocks extending along the lateral sides of the blade contact, the opposing faces of said blocks being tapered so as to lie closely adjacent to the blastimpinging leading edge of said blade contact and appreciably farther away from the trailing edge of said blade contact, and means for causing the interrupting arc to attach itself at said traili ing edge of said blade contact whereby the arc is subjected to the interrupting blast in a comparativeiy wide part of the passage.

6. A gas blast circuit breaker comprising relatively movable contact including a movable bladelike contact, insulating arc chute structure defining an elongated passage at the entrance part of the chute in which said blade contact is reciprocally operated to form an arc gap and which partially encloses said blade contact in sheathlike manner, said chute structure also including insulating arc barriers disposed along said arc gap in transverse edgewise relation thereto so as to form in the chute separate gas passages leading from said are gap, means for directing a blast of interrupting gas at high velocity through said sheath-like passage in a direction substantially transversely of the longitudinal axis thereof so as to traverse the arc gap and drive the are against the adjacent barrier edges, said blade contact being disposed edgewise to said blast, the insulating side walls of said passage extending along the lateral sides of the blade contact being closely positioned with respect to the blast-impinging leading edge of said blade contact and diverging from said edge so that the trailing edge of said blade contact is positioned in a comparatively wide part of the passage, said trailing edge of the blade contact being positioned approximately /2" from the adjacent barrier edges for minimizing arc backpressure, and means for causing the interrupting arc to attach itself at said trailing edge of said blade contact whereby the arc is subjected to the interrupting blast in the aforesaid wide part of the passage opposite said barriers and chute exhaust passages.

7. A gas blast circuit breaker comprising a fixed contact and a coacting relatively movable blade-like contact, an insulating arc chute having barriers forming partitions therein and defining an elongated passage at the entrance part of said chute directly opposite said partitions, said blade contact being reciprocally operable to form an arc gap in said passage, means for directing a blast of interrupting gas at high velocity into said chute through said passage in in a direction subtsantially transversely of the (longitudinal axis thereof so as to drive the are against said partitions, said blade contact being disposed in said passage edgewise to said blast, the insulating passage side walls defining. a

groove that is generally V-shape in cross-sec-.

tion, the blast-impinging leading edge of said blast contact lying along the restricted part of the groove and the trailing edge of said blade contact being positioned in the comparatively wide part thereof, and means for causing the interrupting arc to attach itself at said trailing edge of said blade contact whereby the arc is subjected to the interrupting blast in the aforesaid wlde part of the groove.

ROBERT M. BENNETT. 

